We investigated the expression of vimentin and glial fibrillary acidic protein (GFAP) within Müller cells in normal human retinas and in detached human retinas of proliferative vitreoretinopathy (PVR) cases using the immunogold method. Müller cells in normal retinas showed vimentin immunoreactivity and faint GFAP immunoreactivity; however, in detached retinas they showed distinct GFAP immunoreactivity as well as vimentin immunoreactivity. Immunoelectron microscopic observation revealed that intermediate filaments (IF) within Müller cells in normal retinas showed vimentin immunoreactivity and that those within Müller cells in detached retinas showed both vimentin and GFAP immunoreactivity. Double staining for vimentin and GFAP showed that in detached retinas, these two protein immunoreactivities were observed in the same filaments. These results indicate that IF of human Müller cells consist of vimentin under normal conditions and that Müller cells in detached retinas contain different IF, which consist of vimentin and GFAP.